Hello Irfan,
Honestly, you should ask this question yourself? This is not something that others would be able to advise you.
You should be able to choose the module, based on your education, interest, experience and business process knowledge.
People would advise you 100 things, but at the end of the day, you are the person really needs to work on the module.
Hope this helps.
Kind Regards,
Ravi